1. Field of the Invention
The invention relates to an agitator mill comprising a grinding receptacle defining a grinding chamber, a high-speed agitator disposed in the grinding receptacle, auxiliary grinding bodies at least partially filling the grinding chamber, a grinding-stock/auxiliary-grinding-body inlet opening into the grinding chamber and disposed at one end of the grinding receptacle, an auxiliary-grinding-body retaining device disposed at the other end of the grinding receptacle for grinding stock to be discharged, an auxiliary-grinding-body outlet adjoining the retaining device and disposed upstream of the latter towards the other end of the grinding receptacle, an auxiliary-grinding-body return line leading from the auxiliary-grinding-body outlet to the grinding-stock/auxiliary-grinding-body inlet, a grinding-stock supply line to be passed through in a direction of flow of the grinding stock, and a junction, which--referred to the direction of flow--is disposed upstream of the grinding-stock/auxiliary-grinding-body inlet, and where the grinding-stock supply line and the auxiliary-grinding-body return line are joined to form a grinding-stock supply and auxiliary-grinding-body return line.
2. Background Art
An agitator mill of the generic type is known from U.S. Pat. No. 4,496,106, in which the auxiliary-grinding-body return line opens into the grinding-stock supply line by an angle of 90.degree. directly before the grinding-stock/auxiliary-grinding-body inlet. As a result of the centrifugal effect produced by the agitator unit, the auxiliary grinding bodies and grinding stock not sufficiently milled are to be catapulted off through the auxiliary-grinding-body outlet and returned through the grinding-body return line. By the grinding-body return line opening into the grinding-stock supply line, a suction is to be generated which still supports the centrifugal effect. Further, excellent preliminary mixing of the grinding stock and the auxiliary grinding bodies is to result in the grinding-stock supply line. Experience has shown that any reliable circulation of the auxiliary grinding bodies cannot be ensured by this design of the known agitator mill. The auxiliary grinding bodies get stuck in the auxiliary-grinding-body return line, where they stay. Although, owing to their basic concept, agitator mills of this type have considerable advantages where a high throughput of grinding stock is required that is marked by a considerable transport of auxiliary grinding bodies in the grinding chamber to the separator device, this type of agitator mills has not been successful in practice, because the circulation of the auxiliary grinding bodies does not work.
U.S. Pat. No. 2,595,117 discloses a dry milling ball mill. In this ball mill, the milled grinding stock and the grinding bodies are removed in common through a discharge line and placed into a vertical air duct serving as an air separator. Air is blown from below through this vertical air duct, transporting all the smaller particles into a separator. The grinding balls and the coarse fraction of the grinding stock will fall through the duct against the air stream and are returned to the mill via a conveyor worm. In the separator, sufficiently fine material is once again separated from the grinding stock not sufficiently milled. The latter is likewise fed to the worm via a line.